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The principal reason for a rudder bar over rudder pedals is the load paths in the fuselage. You may notice that planes with rudder bars use much smaller rudder cables. That is because large rudder cables aren't needed with a rudder bar.
With rudder pedals when you press on both pedals (and believe me, you can put a LOT of force on those pedals) the loads are passed through the cables and reacted by the rudder horns and the rudder hinge.
With a rudder bar when you press on both sides the loads are reacted by the pivot pin in the middle of the rudder bar. The cables are sized by the air loads on the rudder, not our size 12 clod hoppers.
The use of rudder bars was a logical one by early designers. The heavy structure to react the pilot foot loads is concentrated at the front of the plane and everything aft of the cockpit can be lightened, the rudder hings, control horns and even the longerons are lighter. The critical design load for the tail can actually be a pilot in a panic jamming both feet down at the same time and it is possible to actually deflect the whole tail cone with that much force. With a rudder bar, all you have to strengthen is the bar mount. Only the difference between the pedal forces passes to the cables and that is limited by the aerodynamic and hinge friction loads.
It really scares me when I see a GL Nieuport with rudder pedals. The first thing I expect to see a failure in is the rudder horns, after that anything goes, including buckling of the longerons. Graham was a pretty good back yard engineer.
Hank
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